1. Field of the Invention
The present invention relates to a method of rerouting connection processing in a communication network system that is capable of multipoint connection to a plurality of subscribers accommodated between a plurality of ATM (Asynchronous Transfer Mode) switches in B-ISDN (Broadband Integrated Service Digital Network).
2. Description of the Related Art
Adoption of B-ISDN (Broadband Integrated Service Digital Network) incorporating ATM (Asynchronous Transfer Mode) technology is currently scheduled for the next-generation communication network. ATM is a system in which digital information that is to be transmitted is divided up into fixed lengths of 48 bytes in each case, to which is added respectively 5-byte control information called a xe2x80x9cheaderxe2x80x9d, these being then transferred by hardware switching. FIG. 21 is a view showing a mode of connection in such B-ISDN. In B-ISDN, in addition to the one-to-one connection mode as in a conventional telephone network shown in FIG. 21A, communication is possible using a multipoint connection, in which the same information can be transmitted simultaneously to a plurality of locations as shown in FIG. 21B.
Specifically, in the case of the one-to-one connection shown in FIG. 21A, when a subscriber a-Sub accommodated on an ATM switching station A is connected with a subscriber b-Sub accommodated on an ATM switching station B, a virtual path (VP) VPAB is set up between station A and station B, and a single virtual channel (VC) VCAB is set up on this virtual path.
Also, in the case of multipoint connection as shown in FIG. 21B, when a connection is made from a subscriber a-Sub accommodated on an ATM switching station A to subscribers b-Sub and c-Sub accommodated on an ATM switching station B and subscribers d-Sub and e-Sub accommodated on an ATM switching station C, respective virtual paths (VP) VPAB and VPAC are set up between station A and station B and between station A and station C and, on these virtual paths VPAB and VPAC, there are set up respectively a single virtual channel VCAB and VCAC.
Let us suppose that, at this point, as shown in FIG. 21C, due to some reason such as a circuit malfunction, connection cannot be performed with station B. In such a case, conventionally, a virtual channel (VC) was set up between station A and station B by setting up a virtual channel VCACB on the virtual path VPAC between station A and station C and the virtual path VPCB between station C and station B. By means of such rerouting connection processing, it was possible to send information from station A simultaneously to stations B and C.
However, the rerouting connection processing described above in fact resulted in setting up two virtual channels VCAC and VCACB on the virtual path VPAC between stations A and C. Thus, if a plurality of virtual channels (VC) was set up on a given virtual path (VP), in cases where the data capacity of the transmitted information was large, such as in the case of image data, or where other virtual channels (VC), not shown, were additionally set up on this virtual path (VP), problems arose such as delayed information transmission, loss of transmission quality, and increased load on the ATM switch, because of exceeding the maximum bandwidth of the virtual path VPAC between stations A and C in FIG. 21C.
In particular, in the case where rerouting connection processing is performed in multipoint connection as described above, as in the case of the two virtual channels VCAC and VCACB that are set up on the virtual path VPAC between station A and station C shown in FIG. 21C, the same information flows on the plurality of virtual channels (VC) of the same virtual path (VP), which is uneconomic. There is therefore a demand, in rerouting connection processing, to set up virtual channels (VC) that are set up on a virtual path (VP) in an efficient manner and to limit the bandwidth capacity of the virtual path (VP).
An object of the present invention is therefore to provide a method of efficient rerouting connection processing in multipoint connection in a communication network that is capable of multipoint connection.
In order to achieve this object, a method of rerouting connection according to the present invention, with a communication network system that is capable of multipoint connection from one switch to a plurality of other switches, if there is a first other switch that cannot receive multipoint connection request information from the one switch, comprises the steps of:
receiving in a second other switch first multipoint connection request information sent from the one switch;
generating in the second other switch second multipoint connection request information to the first other switch by using the first multipoint connection request information;
sending the second multipoint connection request information generated in the second other switch to the first other switch; and
performing prescribed multipoint connection processing in the first other switch by using the second multipoint connection request information sent from the second other switch.
By the method of rerouting connection described above, the second multipoint connection request information to the first other switch is not sent from the one switch to the first other switch via the second other switch, but the second other switch generates the second multipoint connection information and sends this to the first other switch, so the capacity of the circuit that is set up between the one switch and the second switch can be restricted.
Also, in a method of rerouting connection according to the present invention preferably the first multipoint connection request information includes rerouting information, and
in the generating step, the second other switch generates the second multipoint connection request information by using the rerouting information.
For example, the rerouting information includes information of a subscriber who has been requested multipoint connection and is accommodated on the first other switch.
In the case of above, in the generating step, the second other switch generates the second multipoint connection request information containing the information of the subscriber, and
in the performing step ,the first other switch performs multipoint connection processing in respect of the subscriber by using the information of the subscriber.
The rerouting information may include information of the first other switch.
In the case of above, the first multipoint connection request information further includes identification information that identifies a subscriber that has been requested multipoint connection,
in the generating step, the second other switch generates the second multipoint connection request information containing identification information, and
in the performing step ,the first other switch gets information of the subscriber corresponding to the identification information from a data memory means of the first other switch and performs multipoint connection processing in respect of the subscriber by using the information of the subscriber.
Also, the method of rerouting connection of present invention may comprise the additional step of sending rerouting information for generating the second multipoint connection request information to a database that manages the communication network system from the one switch, and
in the generating step, the second other switch gets rerouting information from the database and generates the second multipoint connection request information by using the rerouting information.
In such case, the first multipoint connection request information includes identification information that identifies a subscriber that has been requested multipoint connection, and
in the generating step, the second other switch generates the second multipoint connection request information including the identification information, and
in the performing step ,the first other switch gets the information of the subscriber corresponding to the identification information from the database and performs multipoint connection processing in respect of the subscriber by using the information of the subscriber.
Also, the switches in the present invention may be for example asynchronous transfer mode (ATM) switches.